1. Field of the Invention
The present invention relates to a tandem type rotary generator having two Lundell type rotors disposed tandem to independently generate two voltages of electric power.
2. Description of Related Art
To double electric power generated in a rotary generator, a tandem type rotary generator having two Lundell type rotor cores tandem connected with each other has been proposed in Published Japanese Patent First Publications H01-157251, H05-137295 and H05-308751. In this rotary generator, generation of electric power can be easily controlled, and two voltages can be independently outputted. Therefore, as compared with installation of two generators for outputting two voltages, an installation space and manufacturing cost can be reduced. The tandem type rotary generator independently outputting two voltages is preferably applied as a two-voltage rotary generator wherein a high voltage such as 42V is independently outputted in addition to a normal voltage like 12V.
However, in the conventional tandem type rotary generator, because two power generating sections are disposed in tandem along an axial direction of a rotary shaft, the rotary generator is undesirably lengthened in the axial direction. Further, because the power generating sections acting as two heat sources are disposed near to each other, a spatial density in heat generation is increased, and it is difficult to dispose a cooling system in the generator such that the cooling system effectively dissipates heat from the generator.
For example, when a rotary generator has only a single power generating section, two cooling fans can be disposed on both sides of the power generating section, respectively. Therefore, the cooling fans can effectively cool the single power generating section. However, when a rotary generator has two power generating sections disposed tandem, a single cooling fan can be disposed only on one side of each power generating section in the axial direction. As a result, as compared with a Lundell type rotary generator having only a single power generating section, temperature-sensitive parts such as coils coated with resin are extremely heated up in the tandem type rotary generator. In this case, resin of coils is melted or broken, so that insulation between the coils undesirably deteriorates.